There are presently a variety of procedures utilized for increasing the filling capacity of shredded tobacco tissue including contacting tobacco leaves and/or stems and/or veins with moisture (in the form of water and/or steam) or a solvent and then exposing the thus treated tobacco to heat, a vacuum or freeze-drying so as to cause the tobacco to have an increased filling capacity.
None of the heretofore known procedures has, however, been entirely satisfactory for a variety of reasons. For example, water treatment followed by freeze-drying results in a product which has an objectionable amount of tackiness because of the hygroscopicity of a film-like layer of water-extracted solids which forms on the surface of the tobacco. In many of the heat expansion processes, while there is an initial expansion, the expansion disappears upon drying. The use of solvent expansion has not been entirely suitable since it adds non-tobacco elements to the tobacco.
Most importantly, these prior techniques are not satisfactory in treating a blend of tobaccos to be formed into a final product since they puff the tobacco to such a large extent that it is not possible to form it using the usual apparatus and techniques into stable non-collapsible final products, such as cigarettes. In addition, the prior procedures cannot be used since the cost of the materials and equipment needed is prohibitive. As a consequence, present practice requires that tobacco that has been treated to increase its filling capacity, as by being expanded, must be blended with non-treated tobacco. This is undesirable, particularly since it requires an extra blending step and the maintenance of separate storage facilities for the treated and untreated tobacco.